Add function to retrieve certificates as byte data from the keychain

Author: MatteoPologruto

certificates/install_darwin.go

@@ -139,6 +139,29 @@ const char *evaluateCert(){
     }
     return "";
 }
+
+const char *getCert(){
+    // Each line is a key-value of the dictionary. Note: the the inverted order, value first then key.
+    NSDictionary* dict = [NSDictionary dictionaryWithObjectsAndKeys:
+        (id)kSecClassCertificate, kSecClass,
+        CFSTR("Arduino"), kSecAttrLabel,
+        kSecMatchLimitOne, kSecMatchLimit,
+        kCFBooleanFalse, kSecReturnAttributes,
+        kCFBooleanTrue, kSecReturnData,
+        nil];
+
+    OSStatus err = noErr;
+    CFTypeRef cert;
+    // Use this function to check for errors
+    err = SecItemCopyMatching((CFDictionaryRef)dict, &cert);
+    if (err != errSecItemNotFound){
+        NSString *errString = [@"Error: " stringByAppendingFormat:@"%d", err];
+        NSLog(@"%@", errString);
+        return "";
+    }
+    NSString *certString = [@"" stringByAppendingFormat:@"%d", err];
+    return [certString cStringUsingEncoding:[NSString defaultCStringEncoding]];;
+}
 */
 import "C"
 import (
@@ -195,3 +218,14 @@ func EvaluateCertificates() error {
 	}
 	return nil
 }
+
+// GetCertificate returns a certificate stored in the keychain
+func GetCertificate() ([]byte, error) {
+	log.Infof("Evaluating certificates")
+	p := C.evaluateCert()
+	s := C.GoString(p)
+	if len(s) != 0 {
+		return []byte(s), nil
+	}
+	return nil, nil
+}

certificates/install_default.go

@@ -42,3 +42,9 @@ func EvaluateCertificates() error {
 	log.Warn("platform not supported for the certificates evaluation")
 	return errors.New("platform not supported for the certificates evaluation")
 }
+
+// GetCertificate won't do anything on unsupported Operative Systems
+func GetCertificate() ([]byte, error) {
+	log.Warn("platform not supported for retrieving certificates")
+	return nil, errors.New("platform not supported for retrieving certificates")
+}